Gradual Inflation of Coronal Arcades Building up to Coronal Mass Ejections

Details Gradual Inflation of Coronal Arcades Building up to Coronal Mass Ejections Gradual Inflation of Coronal Arcades Building up to Coronal Mass Ejections

May 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21640604l&link_type=abstract

American Astronomical Society, AAS Meeting #216, #406.04; Bulletin of the American Astronomical Society, Vol. 41, p.880

Astronomy and Astrophysics

Astronomy

Scientific paper

The pre-CME structure is of great importance to understanding the origin of CMEs, which, however, has been largely unknown for CMEs originating from active regions. In this presentation, we investigate this issue using the wavelet-enhanced EUV Imaging Telescope observations combined with the Large Angle and Spectrometric Coronagraph, Michelson Doppler Imager, and GOES soft X-ray observations. Two types of active-region coronal arcades whose gradual inflation may build up to CMEs are identified, namely, post-eruptive arcades and overlying arcades. The observed inflation of 16 selected events sustains for 8.7 +/- 4.1 hours, with the arcade rising from 1.15 +/- 0.06 to 1.36 +/- 0.07 solar radii at a speed of less than 5 km/s, which eventually blast up as a CME similar in morphology to the pre-CME arcade. For the 4 events that were observed on the disk, it is found that the gradual inflation of the arcade is temporally associated with the helicity injection from photosphere. This pre-CME structure is apparently unaffected by the flares occurring during its quasi-static inflation phase, but is closely coupled with the flare occurring during its acceleration phase. In particular, a swirling structure, which is reminiscent of a magnetic flux rope, was observed in one of the arcades over 4 hrs prior to the subsequent CME, and the growth of the arcade is temporally associated with the injection of helicity of opposite sense into the active region via flux emergence. We propose a four-phase evolution paradigm for the observed CMEs, i.e., a quasi-static inflation phase which corresponds to the buildup of magnetic free energy in the corona, followed by the frequently observed three-phase paradigm, including an initial phase, an acceleration phase and a gradual phase.

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